http://journals.iucr.org/a/journalhomepage.html Acta Crystallographica Section A: Foundations of Crystallography publishes papers reporting fundamental advances in all areas of crystallography in the broadest sense. The central themes are, on the one hand, experimental and theoretical studies of the properties and arrangements of atoms, ions and molecules in condensed matter, ideal or real, and of their symmetry and, on the other, the theoretical and experimental aspects of the various methods to determine these arrangements. en-gb Copyright (c) 2008 International Union of Crystallography International Union of Crystallography International Union of Crystallography http://journals.iucr.org urn:issn:0567-7394 Acta Crystallographica Section A: Foundations of Crystallography publishes papers reporting fundamental advances in all areas of crystallography in the broadest sense. The central themes are, on the one hand, experimental and theoretical studies of the properties and arrangements of atoms, ions and molecules in condensed matter, ideal or real, and of their symmetry and, on the other, the theoretical and experimental aspects of the various methods to determine these arrangements. text/html Open access article in Acta Crystallographica Section A Foundations of Crystallography text yearly 6 2002-01-01T00:00+00:00 med@iucr.org Acta Crystallographica Section A Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography urn:issn:0567-7394 http://journals.iucr.org/logos/rss10a.gif http://journals.iucr.org/a/journalhomepage.html Still image http://scripts.iucr.org/cgi-bin/paper?pf0065 Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Müller, U. 2008-07-01 doi:10.1107/S0108767308017042 International Union of Crystallography en BOOK REVIEW text/html Advanced structural inorganic chemistry. IUCr Texts on Crystallography No. 10. By Wai-Kee Li, Gong-Du Zhou and Thomas Chung Wai Mak. Oxford: Oxford University Press, 2008. Pp. xx + 819. Price (paperback) GBP 37.50. ISBN 978-0-19-921695-6. text 4 64 2008-07-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography book reviews 513 514 http://scripts.iucr.org/cgi-bin/paper?pf0060 Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Schreiber, M. 2008-05-01 doi:10.1107/S0108767308009343 International Union of Crystallography en BOOK REVIEW text/html Aperiodic crystals: from modulated phases to quasicrystals. By T. Janssen, G. Chapuis, and M. de Boissieu. IUCr Monographs on Crystallography, No. 20. Oxford: IUCr/Oxford University Press, 2007. Pp. 466. Price GBP 75.00. ISBN 978-0-19-856777-6. text 3 64 2008-05-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography book reviews 433 434 http://scripts.iucr.org/cgi-bin/paper?pf0054 Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Reich, K. 2008-05-01 doi:10.1107/S0108767308006880 International Union of Crystallography en BOOK REVIEW text/html Out of the shadows. Contributions of twentieth-century women to physics. Edited by Nina Byers and Gary Williams. Cambridge: Cambridge University Press, 2006. Pp. xxv + 471. Price (hardback) GBP 30.00. ISBN-13 978-0-521-82197-1. text 3 64 2008-05-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography book reviews 432 432 http://scripts.iucr.org/cgi-bin/paper?pf0058 Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Dodson, G. 2008-03-01 doi:10.1107/S0108767308002407 International Union of Crystallography en BOOK REVIEW text/html J. D. Bernal. The sage of science. By Andrew Brown. Pp. 576. Oxford: Oxford University Press, 2007. Price (paperback) GBP 12.99. ISBN 978-0-19-920565-3 text 2 64 2008-03-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography book reviews 349 351 http://scripts.iucr.org/cgi-bin/paper?es0363 Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 2008-03-01 doi:10.1107/S0108767308002572 International Union of Crystallography en EWALD PRIZE text/html Ewald Prize Award text 2 64 2008-03-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography international union of crystallography 352 352 http://scripts.iucr.org/cgi-bin/paper?pf0039 Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 2008-05-01 doi:10.1107/S0108767308002432 International Union of Crystallography en BOOK RECEIVED text/html Inorganic structural chemistry. By Ulrich Müller. Pp. xi + 268. Chichester: John Wiley & Sons, 2nd ed., 2006. Price (soft cover) GBP 29.95. ISBN 978-0-470-01864-4. text 3 64 2008-05-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography books received 435 435 http://scripts.iucr.org/cgi-bin/paper?me0360 Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Schenk, H. 2008-01-01 doi:10.1107/S0108767307067098 International Union of Crystallography en PREFACE text/html Crystallography Across the Sciences 2 text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography issue preface http://scripts.iucr.org/cgi-bin/paper?sc5024 This paper discusses the trends in the experimental studies of molecular organic solids at high pressures by diffraction techniques. Crystallization of liquids, crystallization from solutions and solid-state transformations are considered. Special attention is paid to the high-pressure studies of pharmaceuticals and of biomimetics. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Boldyreva, E.V. 2008-01-01 doi:10.1107/S0108767307065786 International Union of Crystallography A concise review of the retrospect and prospects of high-pressure diffraction studies of organic crystals, with a special emphasis on pharmaceuticals and biomimetics. en COMPRESSIBILITY; HYDROGEN BONDS; HYDROSTATIC PRESSURES; KINETIC CONTROL; LATTICE STRAIN; PHASE TRANSITIONS; POLYMORPHISM; SOLVENT-MEDIATED TRANSFORMATIONS This paper discusses the trends in the experimental studies of molecular organic solids at high pressures by diffraction techniques. Crystallization of liquids, crystallization from solutions and solid-state transformations are considered. Special attention is paid to the high-pressure studies of pharmaceuticals and of biomimetics. text/html High-pressure diffraction studies of molecular organic solids. A personal view text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 218 231 http://scripts.iucr.org/cgi-bin/paper?sc5018 Structural studies of materials with nano-sized spaces, called nano-structured materials, have been carried out by high-resolution powder diffraction. Our developed analytical method, which is the combination of the maximum-entropy method (MEM) and Rietveld refinement, the so-called MEM/Rietveld method, has been successfully applied to the analysis of synchrotron-radiation (SR) powder diffraction data measured at SPring-8, a third-generation SR light source. In this article, structural studies of nano-porous coordination polymers and endohedral metallofullerenes are presented with the advanced technique of SR powder experiment. The structure of the adsorbed guest molecule in the coordination polymer and encapsulated atoms in the fullerene cage are clearly revealed by the MEM charge density. The methodology of MEM/Rietveld analysis is also presented. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Takata, M. 2008-01-01 doi:10.1107/S010876730706521X International Union of Crystallography The role played by the MEM/Rietveld method, which is a combination of the maximum-entropy method (MEM) and Rietveld analysis, for charge-density studies is described in the structural materials science of novel nano-materials. The atoms' and molecules' charge densities inside the nano-scale spaces of fullerene cages and metal-organic coordination polymers are visualized by using synchrotron-radiation powder data. en CHARGE DENSITY; MAXIMUM-ENTROPY METHOD; METALLOFULLERENE; NANO-MATERIAL; POROUS COORDINATION POLYMERS; POWDER DIFFRACTION; SYNCHROTRON RADIATION Structural studies of materials with nano-sized spaces, called nano-structured materials, have been carried out by high-resolution powder diffraction. Our developed analytical method, which is the combination of the maximum-entropy method (MEM) and Rietveld refinement, the so-called MEM/Rietveld method, has been successfully applied to the analysis of synchrotron-radiation (SR) powder diffraction data measured at SPring-8, a third-generation SR light source. In this article, structural studies of nano-porous coordination polymers and endohedral metallofullerenes are presented with the advanced technique of SR powder experiment. The structure of the adsorbed guest molecule in the coordination polymer and encapsulated atoms in the fullerene cage are clearly revealed by the MEM charge density. The methodology of MEM/Rietveld analysis is also presented. text/html The MEM/Rietveld method with nano-applications – accurate charge-density studies of nano-structured materials by synchrotron-radiation powder diffraction text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 232 245 http://scripts.iucr.org/cgi-bin/paper?sc5021 This review describes the development and application of a new crystallographic technique that is starting to enable the three-dimensional structural determination of molecules in their photo-activated states. So called `photocrystallog­raphy' has wide applicability, particularly in the currently exciting area of photonics, and a discussion of this applied potential is put into context in this article. Studies are classified into four groups: photo-structural changes that are (i) irreversible; (ii) long-lived but reversible under certain conditions; (iii) transient with photo-active lifetimes of the order of microseconds; (iv) very short lived, existing at the nanosecond or even picosecond level. As photo-structural changes relative to the `ground state' can be subtle, this article necessarily concentrates on small-molecule single-crystal X-ray diffraction given that high atomic resolution is possible. That said, where it is pertinent, references are also made to related major advances in photo-induced macromolecular crystallography. The review concludes with an outlook on this new research area, including the future possibility of studying even more ephemeral, femtosecond-lived, photo-active species. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Cole, J.M. 2008-01-01 doi:10.1107/S0108767307065324 International Union of Crystallography A review of crystal-structure determinations of photo-induced molecular species, as derived using small-molecule single-crystal X-ray crystallography, is presented. Such species may be stable or transient, down to picoseconds, and are of substantial interest to the photonics industry. en PHOTOCRYSTALLOGRAPHY This review describes the development and application of a new crystallographic technique that is starting to enable the three-dimensional structural determination of molecules in their photo-activated states. So called `photocrystallog­raphy' has wide applicability, particularly in the currently exciting area of photonics, and a discussion of this applied potential is put into context in this article. Studies are classified into four groups: photo-structural changes that are (i) irreversible; (ii) long-lived but reversible under certain conditions; (iii) transient with photo-active lifetimes of the order of microseconds; (iv) very short lived, existing at the nanosecond or even picosecond level. As photo-structural changes relative to the `ground state' can be subtle, this article necessarily concentrates on small-molecule single-crystal X-ray diffraction given that high atomic resolution is possible. That said, where it is pertinent, references are also made to related major advances in photo-induced macromolecular crystallography. The review concludes with an outlook on this new research area, including the future possibility of studying even more ephemeral, femtosecond-lived, photo-active species. text/html Photocrystallography text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 259 271 http://scripts.iucr.org/cgi-bin/paper?sc5019 Advances made over the past decade in structure determination from powder diffraction data are reviewed with particular emphasis on algorithmic developments and the successes and limitations of the technique. While global optimization methods have been successful in the solution of molecular crystal structures, new methods are required to make the solution of inorganic crystal structures more routine. The use of complementary techniques such as NMR to assist structure solution is discussed and the potential for the combined use of X-ray and neutron diffraction data for structure verification is explored. Structures that have proved difficult to solve from powder diffraction data are reviewed and the limitations of structure determination from powder diffraction data are discussed. Furthermore, the prospects of solving small protein crystal structures over the next decade are assessed. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 David, W.I.F. Shankland, K. 2008-01-01 doi:10.1107/S0108767307064252 International Union of Crystallography Structure determination from powder diffraction data has developed in the past decade to the stage where the structures of many molecular materials, particularly of pharmaceutical interest, are successfully solved. The intrinsically higher symmetry and more complex topology of inorganic materials complicate their structure determination from powder diffraction data which is, as a result, less routine than its molecular counterpart. The study of small proteins from powder diffraction data alone shows great promise and the first structures have been solved. The limits of the powder diffraction technique remain to be explored, particularly if auxiliary techniques are used. en GLOBAL OPTIMIZATION; DIRECT METHODS; POWDER DIFFRACTION; STRUCTURE DETERMINATION Advances made over the past decade in structure determination from powder diffraction data are reviewed with particular emphasis on algorithmic developments and the successes and limitations of the technique. While global optimization methods have been successful in the solution of molecular crystal structures, new methods are required to make the solution of inorganic crystal structures more routine. The use of complementary techniques such as NMR to assist structure solution is discussed and the potential for the combined use of X-ray and neutron diffraction data for structure verification is explored. Structures that have proved difficult to solve from powder diffraction data are reviewed and the limitations of structure determination from powder diffraction data are discussed. Furthermore, the prospects of solving small protein crystal structures over the next decade are assessed. text/html Structure determination from powder diffraction data text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 52 64 http://scripts.iucr.org/cgi-bin/paper?sc5020 A large number of polished stone implements from Palaeolithic to Bronze Age sites of Northern Italy and Southern France are made of high-pressure (HP) metamorphic rocks (eclogite and related rocks), mainly consisting of Na-pyroxene (jadeite to omphacite) from the metamorphic belt of the Western Alps. The standard archaeometric study of prehistoric stone implements follows a procedure that is invasive, expensive and time-consuming. Since Na-pyroxenes may show a large compositional range, a thorough study of the variations affecting the dhkl values, obtained by X-ray diffraction, of three selected reflections as a function of different chemical composition was carried out, in order to determine the chemistry of Na-pyroxene isomorphic mixtures and roughly evaluate their relative amounts. These reflections (\bar221, 310, 002) are sharp, intense and sensitive to the variation of pyroxene chemical composition. Using such dhkl values measured on pyroxenes of known chem­istry, a Ca-pyroxene(Di)–jadeite(Jd)–aegirine(Ae) compositional diagram was constructed, from which the composition of an unknown pyroxene can be estimated within an error of about 5%. When the size of the object is relatively small and a flat polished surface is present, the proposed analytical procedure becomes totally non-invasive. The data obtained shed light on the provenance sources of such implements and the prehistoric trade routes. urn:issn:0108-7673 Giustetto, R. Chiari, G. Compagnoni, R. 2008-01-01 doi:10.1107/S0108767307062691 International Union of Crystallography An innovative non-destructive method is presented for determining the chemistry of Na-pyroxene isomorphic mixtures characterizing Neolithic greenstone implements which permits their provenance and some of the prehistoric trade routes to be traced. en CLINOPYROXENE; COMPOSITIONAL GRID; JADEITE; NEOLITHIC GREENSTONE IMPLEMENTS; OMPHACITE A large number of polished stone implements from Palaeolithic to Bronze Age sites of Northern Italy and Southern France are made of high-pressure (HP) metamorphic rocks (eclogite and related rocks), mainly consisting of Na-pyroxene (jadeite to omphacite) from the metamorphic belt of the Western Alps. The standard archaeometric study of prehistoric stone implements follows a procedure that is invasive, expensive and time-consuming. Since Na-pyroxenes may show a large compositional range, a thorough study of the variations affecting the dhkl values, obtained by X-ray diffraction, of three selected reflections as a function of different chemical composition was carried out, in order to determine the chemistry of Na-pyroxene isomorphic mixtures and roughly evaluate their relative amounts. These reflections (\bar221, 310, 002) are sharp, intense and sensitive to the variation of pyroxene chemical composition. Using such dhkl values measured on pyroxenes of known chem­istry, a Ca-pyroxene(Di)–jadeite(Jd)–aegirine(Ae) compositional diagram was constructed, from which the composition of an unknown pyroxene can be estimated within an error of about 5%. When the size of the object is relatively small and a flat polished surface is present, the proposed analytical procedure becomes totally non-invasive. The data obtained shed light on the provenance sources of such implements and the prehistoric trade routes. text/html An easy non-invasive X-ray diffraction method to determine the composition of Na-pyroxenes from high-density `greenstone' implements text 1 64 168 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography feature articles 161 http://scripts.iucr.org/cgi-bin/paper?sc5016 Since the late 1950's, high-pressure structural studies have become increasingly frequent, following the inception of opposed-anvil cells, development of efficient diffractometric equipment (brighter radiation sources both in laboratories and in synchrotron facilities, highly efficient area detectors) and procedures (for crystal mounting, centring, pressure calibration, collecting and correcting data). Consequently, during the last decades, high-pressure crystallography has evolved into a powerful technique which can be routinely applied in laboratories and dedicated synchrotron and neutron facilities. The variation of pressure adds a new thermodynamic dimension to crystal-structure analyses, and extends the understanding of the solid state and materials in general. New areas of thermodynamic exploration of phase diagrams, polymorphism, transformations between different phases and cohesion forces, structure–property relations, and a deeper understanding of matter at the atomic scale in general are accessible with the high-pressure techniques in hand. A brief history, guidelines and requirements for performing high-pressure structural studies are outlined. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Katrusiak, A. 2008-01-01 doi:10.1107/S0108767307061181 International Union of Crystallography The history and development of high-pressure crystallography are briefly described and examples of structural transformations in compressed compounds are given. The review is focused on the diamond-anvil cell, celebrating its 50th anniversary this year, the principles of its operation and the impact it has had on high-pressure X-ray diffraction. en DIFFRACTION; HIGH PRESSURE; HYDROGEN BONDS; PHASE TRANSITIONS; POLYMORPHISM; THERMODYNAMICS Since the late 1950's, high-pressure structural studies have become increasingly frequent, following the inception of opposed-anvil cells, development of efficient diffractometric equipment (brighter radiation sources both in laboratories and in synchrotron facilities, highly efficient area detectors) and procedures (for crystal mounting, centring, pressure calibration, collecting and correcting data). Consequently, during the last decades, high-pressure crystallography has evolved into a powerful technique which can be routinely applied in laboratories and dedicated synchrotron and neutron facilities. The variation of pressure adds a new thermodynamic dimension to crystal-structure analyses, and extends the understanding of the solid state and materials in general. New areas of thermodynamic exploration of phase diagrams, polymorphism, transformations between different phases and cohesion forces, structure–property relations, and a deeper understanding of matter at the atomic scale in general are accessible with the high-pressure techniques in hand. A brief history, guidelines and requirements for performing high-pressure structural studies are outlined. text/html High-pressure crystallography text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 135 148 http://scripts.iucr.org/cgi-bin/paper?sc5017 The study of crystals at atomic level by electrons – electron crystallography – is an important complement to X-ray crystallography. There are two main advantages of structure determinations by electron crystallography compared to X-ray diffraction: (i) crystals millions of times smaller than those needed for X-ray diffraction can be studied and (ii) the phases of the crystallographic structure factors, which are lost in X-ray diffraction, are present in transmission-electron-microscopy (TEM) images. In this paper, some recent developments of electron crystallography and its applications, mainly on inorganic crystals, are shown. Crystal structures can be solved to atomic resolution in two dimensions as well as in three dimensions from both TEM images and electron diffraction. Different techniques developed for electron crystallography, including three-dimensional reconstruction, the electron precession technique and ultrafast electron crystallography, are reviewed. Examples of electron-crystallography applications are given. There is in principle no limitation to the complexity of the structures that can be solved by electron crystallography. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Zou, X.D. Hovmöller, S. 2008-01-01 doi:10.1107/S0108767307060084 International Union of Crystallography Different techniques for structure determination from transmission electron microscopy and electron diffraction are reviewed, including three-dimensional reconstruction, the precession technique and ultrafast electron crystallography. Examples of electron-crystallography applications are given. en ELECTRON CRYSTALLOGRAPHY; ELECTRON PRECESSION TECHNIQUE; THREE-DIMENSIONAL RECONSTRUCTION; ULTRAFAST ELECTRON CRYSTALLOGRAPHY The study of crystals at atomic level by electrons – electron crystallography – is an important complement to X-ray crystallography. There are two main advantages of structure determinations by electron crystallography compared to X-ray diffraction: (i) crystals millions of times smaller than those needed for X-ray diffraction can be studied and (ii) the phases of the crystallographic structure factors, which are lost in X-ray diffraction, are present in transmission-electron-microscopy (TEM) images. In this paper, some recent developments of electron crystallography and its applications, mainly on inorganic crystals, are shown. Crystal structures can be solved to atomic resolution in two dimensions as well as in three dimensions from both TEM images and electron diffraction. Different techniques developed for electron crystallography, including three-dimensional reconstruction, the electron precession technique and ultrafast electron crystallography, are reviewed. Examples of electron-crystallography applications are given. There is in principle no limitation to the complexity of the structures that can be solved by electron crystallography. text/html Electron crystallography: imaging and single-crystal diffraction from powders text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 149 160 http://scripts.iucr.org/cgi-bin/paper?sc5023 In the paper by Sayre [Acta Cryst. (2008), A64, 33–35], a proposal is made to use stereoscopy as a short-term means of overcoming the primarily technological hurdles involved in three-dimensional imaging of the biological cell by soft X-ray diffraction microscopy. This addendum provides a broader perspective on the techniques used by this rapidly maturing community to investigate structural problems in the biological and material sciences. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Shapiro, D.A. 2008-01-01 doi:10.1107/S0108767307057571 International Union of Crystallography A broad perspective on the techniques used by the coherent X-ray diffraction microscopy community is provided as an addendum to the paper by Sayre [Acta Cryst. (2008), A64, 33–35]. en YEAST CELL; THREE-DIMENSIONAL IMAGING; FLASH IMAGING; SERIAL CRYSTALLOGRAPHY In the paper by Sayre [Acta Cryst. (2008), A64, 33–35], a proposal is made to use stereoscopy as a short-term means of overcoming the primarily technological hurdles involved in three-dimensional imaging of the biological cell by soft X-ray diffraction microscopy. This addendum provides a broader perspective on the techniques used by this rapidly maturing community to investigate structural problems in the biological and material sciences. text/html Report on a project on three-dimensional imaging of the biological cell by single-particle X-ray diffraction. Addendum text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 36 37 http://scripts.iucr.org/cgi-bin/paper?sc5022 Single-particle X-ray diffraction is an extension of X-ray crystallography which allows the specimen to be any small solid-state bounded object; in Shapiro et al. [Proc. Natl Acad. Sci. USA (2005), 102, 15343–15346] and Thibault et al. [Acta Cryst. (2006), A62, 248–261], the reader can find descriptions of a recent StonyBrook/Berkeley/Cornell two-dimensional imaging of a yeast cell by this technique. Our present work is aimed at extending the technique to the three-dimensional imaging of a cell. However, the usual method of doing that, namely rotating the specimen into many orientations in the X-ray beam, has not as yet given sufficiently good three-dimensional diffraction data to allow the work to go forward, the largest problem being the difficulty of preventing unwanted levels of change in the specimen through the extended exposure to a hostile environment of X-rays and, in some cases, high vacuum and/or extreme cold. The present paper discusses possible methods of dealing with this problem. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Sayre, D. 2008-01-01 doi:10.1107/S010876730705550X International Union of Crystallography In biocellular imaging, unwanted changes in the specimen during the longer exposures for three-dimensional data collection are making the step from two- to three-dimensional imaging difficult. Low-exposure stereoscopic three-dimensional imaging may be one answer to the problem. en YEAST CELL; THREE-DIMENSIONAL IMAGING; STEREOSCOPIC IMAGING Single-particle X-ray diffraction is an extension of X-ray crystallography which allows the specimen to be any small solid-state bounded object; in Shapiro et al. [Proc. Natl Acad. Sci. USA (2005), 102, 15343–15346] and Thibault et al. [Acta Cryst. (2006), A62, 248–261], the reader can find descriptions of a recent StonyBrook/Berkeley/Cornell two-dimensional imaging of a yeast cell by this technique. Our present work is aimed at extending the technique to the three-dimensional imaging of a cell. However, the usual method of doing that, namely rotating the specimen into many orientations in the X-ray beam, has not as yet given sufficiently good three-dimensional diffraction data to allow the work to go forward, the largest problem being the difficulty of preventing unwanted levels of change in the specimen through the extended exposure to a hostile environment of X-rays and, in some cases, high vacuum and/or extreme cold. The present paper discusses possible methods of dealing with this problem. text/html Report on a project on three-dimensional imaging of the biological cell by single-particle X-ray diffraction text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 33 35 http://scripts.iucr.org/cgi-bin/paper?sc5013 The morphotropic phase boundary in the phase diagram of the technologically important Pb(ZrxTi1−x)O3 (PZT) ceramics has been traditionally believed to separate ferroelectric tetragonal and rhombohedral phase regions. This old picture has come under close scrutiny during the last eight years following the discovery of new monoclinic phases in the Cm and Cc space groups. This article presents a brief overview of these discoveries in which the use of multiple diffraction probes (X-ray, electron, neutron diffraction) in conjunction with physical property measurements has played a crucial role. A new phase diagram of PZT showing the stability fields of these structures below room temperature is also presented. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Pandey, D. Singh, A.K. Baik, S. 2008-01-01 doi:10.1107/S0108767307055511 International Union of Crystallography An overview of the recent discoveries of the monoclinic phases in the Cm and Cc space groups and their stability fields in the Pb(ZrxTi1−x)O3 phase diagram is presented. en FERROIC PHASES; PIEZOELECTRIC PB(ZRXTI1-X)O3 CERAMICS (PZT) The morphotropic phase boundary in the phase diagram of the technologically important Pb(ZrxTi1−x)O3 (PZT) ceramics has been traditionally believed to separate ferroelectric tetragonal and rhombohedral phase regions. This old picture has come under close scrutiny during the last eight years following the discovery of new monoclinic phases in the Cm and Cc space groups. This article presents a brief overview of these discoveries in which the use of multiple diffraction probes (X-ray, electron, neutron diffraction) in conjunction with physical property measurements has played a crucial role. A new phase diagram of PZT showing the stability fields of these structures below room temperature is also presented. text/html Stability of ferroic phases in the highly piezoelectric Pb(ZrxTi1−x)O3 ceramics text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 192 203 http://scripts.iucr.org/cgi-bin/paper?pf0061 Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Rutherford, J.S. 2008-03-01 doi:10.1107/S0108767308002419 International Union of Crystallography en BOOK REVIEW text/html Theories and techniques of crystal structure determination. By Uri Shmueli, Pp. 269. Oxford: Oxford University Press, 2007. Price GBP 32.50. ISBN 978-0-19-921350-4. text 2 64 2008-03-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography book reviews 348 348 http://scripts.iucr.org/cgi-bin/paper?sc5014 The 2003 outbreak of severe acute respiratory syndrome (SARS), caused by a previously unknown coronavirus called SARS-CoV, had profound social and economic impacts worldwide. Since then, structure–function studies of SARS-CoV proteins have provided a wealth of information that increases our understanding of the underlying mechanisms of SARS. While no effective therapy is currently available, considerable efforts have been made to develop vaccines and drugs to prevent SARS-CoV infection. In this review, some of the notable achievements made by SARS structural biology projects worldwide are examined and strategies for therapeutic intervention are discussed based on available SARS-CoV protein structures. To date, 12 structures have been determined by X-ray crystallography or NMR from the 28 proteins encoded by SARS-CoV. One key protein, the SARS-CoV main protease (Mpro), has been the focus of considerable structure-based drug discovery efforts. This article highlights the importance of structural biology and shows that structures for drug design can be rapidly determined in the event of an emerging infectious disease. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Bartlam, M. Xue, X. Rao, Z. 2008-01-01 doi:10.1107/S0108767307054426 International Union of Crystallography The severe acute respiratory syndrome (SARS) coronavirus outbreak in 2003 had profound social and economic impacts worldwide. This review highlights the importance of structural biology and shows that structures for drug design can be rapidly determined in the event of an emerging infectious disease. en DRUG DESIGN; SARS CORONAVIRUS; SARS-COV The 2003 outbreak of severe acute respiratory syndrome (SARS), caused by a previously unknown coronavirus called SARS-CoV, had profound social and economic impacts worldwide. Since then, structure–function studies of SARS-CoV proteins have provided a wealth of information that increases our understanding of the underlying mechanisms of SARS. While no effective therapy is currently available, considerable efforts have been made to develop vaccines and drugs to prevent SARS-CoV infection. In this review, some of the notable achievements made by SARS structural biology projects worldwide are examined and strategies for therapeutic intervention are discussed based on available SARS-CoV protein structures. To date, 12 structures have been determined by X-ray crystallography or NMR from the 28 proteins encoded by SARS-CoV. One key protein, the SARS-CoV main protease (Mpro), has been the focus of considerable structure-based drug discovery efforts. This article highlights the importance of structural biology and shows that structures for drug design can be rapidly determined in the event of an emerging infectious disease. text/html The search for a structural basis for therapeutic intervention against the SARS coronavirus text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 204 213 http://scripts.iucr.org/cgi-bin/paper?sc5012 As the first centennial of X-ray diffraction is inevitably drawing closer, it is tempting to reflect on the impact that this fascinating discipline has had on natural sciences and how it has changed the world we live in. Also, next year is the 160th anniversary of the fateful April afternoon when Louis Pasteur separated d- from l-tartrate crystals, an event that many science historians recognize as the birth of stereochemistry, and the first step that the barely nascent field of crystallography took on the road to elucidate a fundamental phenomenon of chemistry and biology – chirality. Many great minds – Pasteur, Van 't Hoff, Fischer, Lord Kelvin, the Braggs, Astbury and Bijvoet, to mention just a few – contributed along the way. But one central inanimate character was there at all times – an inconspicuous somewhat obscure organic compound found in wine: tartaric acid. This is the story of its contribution to science. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Derewenda, Z.S. 2008-01-01 doi:10.1107/S0108767307054293 International Union of Crystallography How tartaric acid, an inconspicuous organic compound found in wine, made a pivotal contribution to structural chemistry and biology. en CHIRALITY; TARTARIC ACID As the first centennial of X-ray diffraction is inevitably drawing closer, it is tempting to reflect on the impact that this fascinating discipline has had on natural sciences and how it has changed the world we live in. Also, next year is the 160th anniversary of the fateful April afternoon when Louis Pasteur separated d- from l-tartrate crystals, an event that many science historians recognize as the birth of stereochemistry, and the first step that the barely nascent field of crystallography took on the road to elucidate a fundamental phenomenon of chemistry and biology – chirality. Many great minds – Pasteur, Van 't Hoff, Fischer, Lord Kelvin, the Braggs, Astbury and Bijvoet, to mention just a few – contributed along the way. But one central inanimate character was there at all times – an inconspicuous somewhat obscure organic compound found in wine: tartaric acid. This is the story of its contribution to science. text/html On wine, chirality and crystallography text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 246 258 http://scripts.iucr.org/cgi-bin/paper?sc5015 The history of crystallographic computing and use of crystallographic software is one which traces the escape from the drudgery of manual human calculations to a world where the user delegates most of the travail to electronic computers. In practice, this involves practising crystallographers communicating their thoughts to the crystallographic program authors, in the hope that new procedures will be implemented within their software. Against this background, the development of small-molecule single-crystal and powder diffraction software is traced. Starting with the analogue machines and the use of Hollerith tabulators of the late 1930's, it is shown that computing developments have been science led, with new technologies being harnessed to solve pressing crystallographic problems. The development of software is also traced, with a final caution that few of the computations now performed daily are really understood by the program users. Unless a sufficient body of people continues to dismantle and re-build programs, the knowledge encoded in the old programs will become as inaccessible as the knowledge of how to build the Great Pyramid at Giza. urn:issn:0108-7673 Cranswick, L.M.D. 2008-01-01 doi:10.1107/S0108767307051355 International Union of Crystallography The history of crystallographic computing and use of crystallographic software is one which traces the escape from the drudgery of manual human calculations to a world where the user delegates most of the travail to electronic computers. This review traces the development of small-molecule single-crystal and powder diffraction hardware, starting with the use of Hollerith tabulators of the late 1930's through to today's use of high-performance personal computers. It also emphasizes that the main challenge for current and future crystallography computing is not that of hardware development, or even specific scientific challenges, but rather in maintaining a critical mass of human expertise with which these computational challenges can be undertaken. en BEEVERS; COMRIE; ECKERT; HISTORY; HOLLERITH; PAULING; POWDER DIFFRACTION; SINGLE CRYSTAL; SOFTWARE; TEACHING The history of crystallographic computing and use of crystallographic software is one which traces the escape from the drudgery of manual human calculations to a world where the user delegates most of the travail to electronic computers. In practice, this involves practising crystallographers communicating their thoughts to the crystallographic program authors, in the hope that new procedures will be implemented within their software. Against this background, the development of small-molecule single-crystal and powder diffraction software is traced. Starting with the analogue machines and the use of Hollerith tabulators of the late 1930's, it is shown that computing developments have been science led, with new technologies being harnessed to solve pressing crystallographic problems. The development of software is also traced, with a final caution that few of the computations now performed daily are really understood by the program users. Unless a sufficient body of people continues to dismantle and re-build programs, the knowledge encoded in the old programs will become as inaccessible as the knowledge of how to build the Great Pyramid at Giza. text/html Busting out of crystallography's Sisyphean prison: from pencil and paper to structure solving at the press of a button: past, present and future of crystallographic software development, maintenance and distribution text 1 64 87 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography feature articles 65 http://scripts.iucr.org/cgi-bin/paper?sc5002 Methods of contrast variation are tools that are essential in macromolecular structure research. Anomalous dispersion of X-ray diffraction is widely used in protein crystallography. Recent attempts to extend this method to native resonant labels like sulfur and phosphorus are promising. Substitution of hydrogen isotopes is central to biological applications of neutron scattering. Proton spin polarization considerably enhances an existing contrast prepared by isotopic substitution. Concepts and methods of nuclear magnetic resonance (NMR) become an important ingredient in neutron scattering from dynamically polarized targets. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Stuhrmann, H.B. 2008-01-01 doi:10.1107/S0108767307046569 International Union of Crystallography Originally conceived for protein crystallography, contrast variation has become a favourite tool of small-angle scattering. Recent developments in contrast variation are reviewed. en ANOMALOUS DISPERSION; DYNAMIC NUCLEAR POLARIZATION; ISOTOPIC SUBSTITUTION; UNIQUENESS Methods of contrast variation are tools that are essential in macromolecular structure research. Anomalous dispersion of X-ray diffraction is widely used in protein crystallography. Recent attempts to extend this method to native resonant labels like sulfur and phosphorus are promising. Substitution of hydrogen isotopes is central to biological applications of neutron scattering. Proton spin polarization considerably enhances an existing contrast prepared by isotopic substitution. Concepts and methods of nuclear magnetic resonance (NMR) become an important ingredient in neutron scattering from dynamically polarized targets. text/html Small-angle scattering and its interplay with crystallography, contrast variation in SAXS and SANS text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 181 191 http://scripts.iucr.org/cgi-bin/paper?sc5009 This paper summarizes the current state of charge flipping, a recently developed algorithm of ab initio structure determination. Its operation is based on the perturbation of large plateaus of low electron density but not directly on atomicity. Such a working principle radically differs from that of classical direct methods and offers complementary applications. The list of successful structure-solution cases includes periodic and aperiodic crystals using single-crystal and powder diffraction data measured with X-ray and neutron radiation. Apart from counting applications, the paper mainly deals with algorithmic issues: it describes and compares new variants of the iteration scheme, helps to identify and improve solutions, discusses the required data and the use of known information. Finally, it tries to foretell the future of such an alternative among well established direct methods. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Oszlányi, G. Sütő, A. 2008-01-01 doi:10.1107/S0108767307046028 International Union of Crystallography The current state of the charge flipping algorithm is reviewed. en AB INITIO STRUCTURE DETERMINATION; CHARGE FLIPPING ALGORITHM This paper summarizes the current state of charge flipping, a recently developed algorithm of ab initio structure determination. Its operation is based on the perturbation of large plateaus of low electron density but not directly on atomicity. Such a working principle radically differs from that of classical direct methods and offers complementary applications. The list of successful structure-solution cases includes periodic and aperiodic crystals using single-crystal and powder diffraction data measured with X-ray and neutron radiation. Apart from counting applications, the paper mainly deals with algorithmic issues: it describes and compares new variants of the iteration scheme, helps to identify and improve solutions, discusses the required data and the use of known information. Finally, it tries to foretell the future of such an alternative among well established direct methods. text/html The charge flipping algorithm text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 123 134 http://scripts.iucr.org/cgi-bin/paper?sc5008 The journals of the International Union of Crystallography have grown in size and number over the past 60 years to match developments in scientific practice and technique. High quality of publication has always been at the forefront of editorial policy and ways in which this has been achieved are described. In particular, the development of standard exchange and archive formats for crystallographic data has allowed the editorial office to conduct automated analyses of structural data supporting articles submitted for publication and these analyses assist the scientific editors in careful and critical peer review. The new information technologies of the Internet age have allowed the IUCr journals to flourish and to provide a wide range of powerful services to authors, editors and readers alike. The integration of literature and supporting structural data is of particular importance. The new technologies have also brought fresh economic and cultural challenges, and offer completely new opportunities to disseminate the results of scientific research. The journals continue to respond to these challenges and take advantage of new opportunities in innovative ways. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Strickland, P.R. McMahon, B. 2008-01-01 doi:10.1107/S0108767307045801 International Union of Crystallography The journal publishing activities of the IUCr over the past 60 years are described, together with the new technological, economic and cultural challenges faced by the journals. Particular emphasis is placed on the role of innovative publishing technologies in ensuring the quality of the published information and in providing effective access to the data underpinning the scientific results. en CRYSTALLOGRAPHIC PUBLISHING; IUCR JOURNALS The journals of the International Union of Crystallography have grown in size and number over the past 60 years to match developments in scientific practice and technique. High quality of publication has always been at the forefront of editorial policy and ways in which this has been achieved are described. In particular, the development of standard exchange and archive formats for crystallographic data has allowed the editorial office to conduct automated analyses of structural data supporting articles submitted for publication and these analyses assist the scientific editors in careful and critical peer review. The new information technologies of the Internet age have allowed the IUCr journals to flourish and to provide a wide range of powerful services to authors, editors and readers alike. The integration of literature and supporting structural data is of particular importance. The new technologies have also brought fresh economic and cultural challenges, and offer completely new opportunities to disseminate the results of scientific research. The journals continue to respond to these challenges and take advantage of new opportunities in innovative ways. text/html Crystallographic publishing in the electronic age text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 38 51 http://scripts.iucr.org/cgi-bin/paper?sc5006 Mathematical crystallography is the branch of crystallography dealing specifically with the fundamental properties of symmetry and periodicity of crystals, topological properties of crystal structures, twins, modular and modulated structures, polytypes and OD structures, as well as the symmetry aspects of phase transitions and physical properties of crystals. Mathematical crystallography has had its most evident success with the development of the theory of space groups at the end of the XIX century; since then, it has greatly enlarged its applications, but crystallographers are not always familiar with the developments that followed, partly because the applications sometimes require some additional background that the structural crystallographer does not always possess (as is the case, for example, in graph theory). The knowledge offered by mathematical crystallography is at present only partly mirrored in International Tables for Crystallography and is sometimes still enshrined in more specialist texts and publications. To cover this communication gap is one of the tasks of the IUCr Commission on Mathematical and Theoretical Crystallography (MaThCryst). Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Nespolo, M. 2008-01-01 doi:10.1107/S0108767307044625 International Union of Crystallography A survey of some of the main topics of mathematical crystallography is presented, together with the challenges for future developments. en GRAPH THEORY; MATHEMATICAL CRYSTALLOGRAPHY; OD STRUCTURES; POLYTYPES; SYMMETRY; THEORETICAL CRYSTALLOGRAPHY; TOPOLOGY; TWINS Mathematical crystallography is the branch of crystallography dealing specifically with the fundamental properties of symmetry and periodicity of crystals, topological properties of crystal structures, twins, modular and modulated structures, polytypes and OD structures, as well as the symmetry aspects of phase transitions and physical properties of crystals. Mathematical crystallography has had its most evident success with the development of the theory of space groups at the end of the XIX century; since then, it has greatly enlarged its applications, but crystallographers are not always familiar with the developments that followed, partly because the applications sometimes require some additional background that the structural crystallographer does not always possess (as is the case, for example, in graph theory). The knowledge offered by mathematical crystallography is at present only partly mirrored in International Tables for Crystallography and is sometimes still enshrined in more specialist texts and publications. To cover this communication gap is one of the tasks of the IUCr Commission on Mathematical and Theoretical Crystallography (MaThCryst). text/html Does mathematical crystallography still have a role in the XXI century? text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 96 111 http://scripts.iucr.org/cgi-bin/paper?sc5010 An account is given of the development of the SHELX system of computer programs from SHELX-76 to the present day. In addition to identifying useful innovations that have come into general use through their implementation in SHELX, a critical analysis is presented of the less-successful features, missed opportunities and desirable improvements for future releases of the software. An attempt is made to understand how a program originally designed for photographic intensity data, punched cards and computers over 10000 times slower than an average modern personal computer has managed to survive for so long. SHELXL is the most widely used program for small-molecule refinement and SHELXS and SHELXD are often employed for structure solution despite the availability of objectively superior programs. SHELXL also finds a niche for the refinement of macromolecules against high-resolution or twinned data; SHELXPRO acts as an interface for macromolecular applications. SHELXC, SHELXD and SHELXE are proving useful for the experimental phasing of macromolecules, especially because they are fast and robust and so are often employed in pipelines for high-throughput phasing. This paper could serve as a general literature citation when one or more of the open-source SHELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Sheldrick, G.M. 2008-01-01 doi:10.1107/S0108767307043930 International Union of Crystallography The SHELX programs for crystal structure determination are reviewed by their author. en COMPUTER PROGRAMS; CRYSTAL STRUCTURE DETERMINATION; PHASING; SHELX; STRUCTURE REFINEMENT An account is given of the development of the SHELX system of computer programs from SHELX-76 to the present day. In addition to identifying useful innovations that have come into general use through their implementation in SHELX, a critical analysis is presented of the less-successful features, missed opportunities and desirable improvements for future releases of the software. An attempt is made to understand how a program originally designed for photographic intensity data, punched cards and computers over 10000 times slower than an average modern personal computer has managed to survive for so long. SHELXL is the most widely used program for small-molecule refinement and SHELXS and SHELXD are often employed for structure solution despite the availability of objectively superior programs. SHELXL also finds a niche for the refinement of macromolecules against high-resolution or twinned data; SHELXPRO acts as an interface for macromolecular applications. SHELXC, SHELXD and SHELXE are proving useful for the experimental phasing of macromolecules, especially because they are fast and robust and so are often employed in pipelines for high-throughput phasing. This paper could serve as a general literature citation when one or more of the open-source SHELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination. text/html A short history of SHELX text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 112 122 http://scripts.iucr.org/cgi-bin/paper?sc5011 Following the seminal work of Von Dreele, powder X-ray diffraction studies on proteins are being established as a valuable complementary technique to single-crystal measurements. A wide range of small proteins have been found to give synchrotron powder diffraction profiles where the peak widths are essentially limited only by the instrumental resolution. The rich information contained in these profiles, combined with developments in data analysis, has stimulated research and development to apply the powder technique to microcrystalline protein samples. In the present work, progress in using powder diffraction for macromolecular crystallography is reported. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Margiolaki, I. Wright, J.P. 2008-01-01 doi:10.1107/S0108767307043735 International Union of Crystallography The last 10 years have seen a revolution in powder crystallography; macromolecules can now be studied using powder samples. When large single crystals are not available then crystallographic information may be obtained from a polycrystalline powder instead. en POWDER DIFFRACTION; PROTEIN CRYSTALLOGRAPHY; SYNCHROTRON RADIATION Following the seminal work of Von Dreele, powder X-ray diffraction studies on proteins are being established as a valuable complementary technique to single-crystal measurements. A wide range of small proteins have been found to give synchrotron powder diffraction profiles where the peak widths are essentially limited only by the instrumental resolution. The rich information contained in these profiles, combined with developments in data analysis, has stimulated research and development to apply the powder technique to microcrystalline protein samples. In the present work, progress in using powder diffraction for macromolecular crystallography is reported. text/html Powder crystallography on macromolecules text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 169 180 http://scripts.iucr.org/cgi-bin/paper?sc5005 Neutron diffraction provides an experimental method of directly locating H atoms in proteins, a technique complementary to ultra-high-resolution X-ray diffraction. Three different types of neutron diffractometers for biological macromolecules have been constructed in Japan, France and the USA, and they have been used to determine the crystal structures of proteins up to resolution limits of 1.5–2.5 Å. Results relating to H-atom positions and hydration patterns in proteins have been obtained from these studies. Examples include the geometrical details of hydrogen bonds, the role of H atoms in enzymatic activity, CH3 configuration, H/D exchange in proteins and oligonucleotides, and the dynamical behavior of hydration structures, all of which have been extracted from these structural results and reviewed. Other techniques, such as the growth of large single crystals and a database of hydrogen and hydration in proteins, are described. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Niimura, N. Bau, R. 2008-01-01 doi:10.1107/S0108767307043498 International Union of Crystallography Several results from neutron protein crystallography relating H-atom positions and hydration patterns in proteins and oligonucleotides are reviewed. en BIOLOGICAL MACROMOLECULES; FOLDING STRUCTURE; NEUTRON PROTEIN CRYSTALLOGRAPHY Neutron diffraction provides an experimental method of directly locating H atoms in proteins, a technique complementary to ultra-high-resolution X-ray diffraction. Three different types of neutron diffractometers for biological macromolecules have been constructed in Japan, France and the USA, and they have been used to determine the crystal structures of proteins up to resolution limits of 1.5–2.5 Å. Results relating to H-atom positions and hydration patterns in proteins have been obtained from these studies. Examples include the geometrical details of hydrogen bonds, the role of H atoms in enzymatic activity, CH3 configuration, H/D exchange in proteins and oligonucleotides, and the dynamical behavior of hydration structures, all of which have been extracted from these structural results and reviewed. Other techniques, such as the growth of large single crystals and a database of hydrogen and hydration in proteins, are described. text/html Neutron protein crystallography: beyond the folding structure of biological macromolecules text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 12 22 http://scripts.iucr.org/cgi-bin/paper?sc5007 Studies of diffuse scattering had a prominent place in the first issue of Acta Crystallographica 60 years ago at a time when conventional crystallography (determination of the average structure from Bragg peaks) was in its infancy. Since that time, conventional crystallography has developed enormously while diffuse-scattering analysis has seemingly lagged well behind. The paper highlights some of the extra difficulties involved in the measurement, interpretation and analysis of diffuse scattering and plots the progress that has been made. With the advent of the latest X-ray and neutron sources, area detectors and the ever-increasing power of computers, most disorder problems are now tractable. Two recent contrasting examples are described which highlight what can be achieved by current methods. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Welberry, T.R. Goossens, D.J. 2008-01-01 doi:10.1107/S0108767307041918 International Union of Crystallography The paper highlights some of the extra difficulties involved in the measurement, interpretation and analysis of diffuse scattering relative to the methods of conventional crystallography and plots the progress that has been made in the lifetime of Acta Crystallographica. With the advent of the latest X-ray and neutron sources, area detectors and the ever-increasing power of computers, most diffuse scattering and disorder problems are now tractable. en DIFFUSE SCATTERING; MONTE CARLO METHODS Studies of diffuse scattering had a prominent place in the first issue of Acta Crystallographica 60 years ago at a time when conventional crystallography (determination of the average structure from Bragg peaks) was in its infancy. Since that time, conventional crystallography has developed enormously while diffuse-scattering analysis has seemingly lagged well behind. The paper highlights some of the extra difficulties involved in the measurement, interpretation and analysis of diffuse scattering and plots the progress that has been made. With the advent of the latest X-ray and neutron sources, area detectors and the ever-increasing power of computers, most disorder problems are now tractable. Two recent contrasting examples are described which highlight what can be achieved by current methods. text/html The interpretation and analysis of diffuse scattering using Monte Carlo simulation methods text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 23 32 http://scripts.iucr.org/cgi-bin/paper?pf0062 Copyright (c) 2007 International Union of Crystallography urn:issn:0108-7673 Paufler, P. 2007-11-01 doi:10.1107/S0108767307041207 International Union of Crystallography en BOOK REVIEW text/html Complete online set of International tables for crystallography, Vols. A–G. Edited by H. Fuess, Th. Hahn, H. Wondratschek, U. Müller, U. Shmueli, E. Prince, A. Authier, V. Kopský, D. B. Litvin, M. G. Rossmann, E. Arnold, S. Hall and B. McMahon. Springer, jointly published with the IUCr, 2007. Price for online access USD 2080.00. eISBN: 978-1-4020-5259-0, doi: 10.1107/97809553602060000001, http://it.iucr.org. text 6 63 2007-11-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2007 International Union of Crystallography book reviews 483 483 http://scripts.iucr.org/cgi-bin/paper?sc5001 Crystallographic Nexus CD-ROMs, containing a range of free crystallographic software for single-crystal and powder diffraction available on the Internet, have been distributed on request since 1996. The free CD is made in the form of a `virtual Internet' with the main intent of benefiting crystallographers with inadequate Internet access. The IUCr funds an annual/biennial update which is distributed to known previous recipients. Feedback from current recipients indicates the CD is still useful. The most current IUCr-funded CD is being produced by the CCP14 project at University College London and The Royal Institution UK for distribution to the ECM 2007 and AsCA 2007 conferences. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Cranswick, L.M.D. Bisson, W. Cockcroft, J.K. 2008-01-01 doi:10.1107/S0108767307040573 International Union of Crystallography Crystallographic Nexus CD-ROMs, containing a range of free crystallographic software for single-crystal and powder diffraction available on the Internet, have been distributed free on request since 1996. The free CD is made in the form of a `virtual Internet' with the main intent of benefiting crystallographers with inadequate Internet access. en CD-ROM; CRYSTALLOGRAPHIC SOFTWARE; INTERNET; POWDER DIFFRACTION; SINGLE CRYSTAL Crystallographic Nexus CD-ROMs, containing a range of free crystallographic software for single-crystal and powder diffraction available on the Internet, have been distributed on request since 1996. The free CD is made in the form of a `virtual Internet' with the main intent of benefiting crystallographers with inadequate Internet access. The IUCr funds an annual/biennial update which is distributed to known previous recipients. Feedback from current recipients indicates the CD is still useful. The most current IUCr-funded CD is being produced by the CCP14 project at University College London and The Royal Institution UK for distribution to the ECM 2007 and AsCA 2007 conferences. text/html Nexus, crystallographic computing all around the world text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 214 217 http://scripts.iucr.org/cgi-bin/paper?es0361 Copyright (c) 2007 International Union of Crystallography urn:issn:0108-7673 Helliwell, J.R. Abrahams, S.C. 2007-09-01 doi:10.1107/S0108767307039062 International Union of Crystallography en OBITUARIES text/html Durward William John Cruickshank (1924–2007) text 5 63 2007-09-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2007 International Union of Crystallography obituaries 375 379 http://scripts.iucr.org/cgi-bin/paper?sc5003 It took Dan Shechtman more than two years to get his discovery of an Al–Mn phase with icosahedral diffraction symmetry and sharp Bragg reflections published. A paradigm shift had to take place before this novel ordering state of matter – seemingly contradicting crystallographic laws – could be accepted. Today, more than 25 years later, the existence of quasicrystals is beyond doubt. However, not everything is settled yet. All the factors governing formation, growth, stability and structure of quasicrystals are still not fully understood, nor is it resolved whether their structures are strictly or only on average quasiperiodic, and it is still an open question why only quasicrystals with 5-, 8-, 10- and 12-fold rotational symmetry have been experimentally observed so far. These points will be addressed in this review article. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Steurer, W. Deloudi, S. 2008-01-01 doi:10.1107/S0108767307038627 International Union of Crystallography The state of the art of structure research on quasicrystals is reviewed. Some questions concerning formation, growth and stability are addressed. en DECAGONAL PHASES; ICOSAHEDRAL PHASES; N-DIMENSIONAL APPROACH; PHOTONIC QUASICRYSTALS; QUASICRYSTALS It took Dan Shechtman more than two years to get his discovery of an Al–Mn phase with icosahedral diffraction symmetry and sharp Bragg reflections published. A paradigm shift had to take place before this novel ordering state of matter – seemingly contradicting crystallographic laws – could be accepted. Today, more than 25 years later, the existence of quasicrystals is beyond doubt. However, not everything is settled yet. All the factors governing formation, growth, stability and structure of quasicrystals are still not fully understood, nor is it resolved whether their structures are strictly or only on average quasiperiodic, and it is still an open question why only quasicrystals with 5-, 8-, 10- and 12-fold rotational symmetry have been experimentally observed so far. These points will be addressed in this review article. text/html Fascinating quasicrystals text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 1 11 http://scripts.iucr.org/cgi-bin/paper?sh0188 Both the approach used and the progress made in the assignment of structure types to the crystal structures contained in the ICSD database are reported. Extending earlier work, an hierarchical set of criteria for the separation of isopointal structures into isoconfigurational structure types is used. It is shown how these criteria, which include the space group (number), Wyckoff sequence and Pearson symbol, c/a ratio, β ranges, ANX formulae and, in certain cases, the necessary elements and forbidden elements, may be used to uniquely identify the representative structure types of the compounds contained in the ICSD database. Copyright (c) 2007 International Union of Crystallography urn:issn:0108-7673 Allmann, R. Hinek, R. 2007-09-01 doi:10.1107/S0108767307038081 International Union of Crystallography The approach used and the progress made in the assignment of structure types to the crystal structures contained in the ICSD database are reported. en INORGANIC CRYSTAL STRUCTURE DATABASE; ICSD; STRUCTURE TYPES Both the approach used and the progress made in the assignment of structure types to the crystal structures contained in the ICSD database are reported. Extending earlier work, an hierarchical set of criteria for the separation of isopointal structures into isoconfigurational structure types is used. It is shown how these criteria, which include the space group (number), Wyckoff sequence and Pearson symbol, c/a ratio, β ranges, ANX formulae and, in certain cases, the necessary elements and forbidden elements, may be used to uniquely identify the representative structure types of the compounds contained in the ICSD database. text/html The introduction of structure types into the Inorganic Crystal Structure Database ICSD text 5 63 2007-09-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2007 International Union of Crystallography research papers 412 417 http://scripts.iucr.org/cgi-bin/paper?sc5004 The Protein Data Bank began as a grassroots effort in 1971. It has grown from a small archive containing a dozen structures to a major international resource for structural biology containing more than 40000 entries. The interplay of science, technology and attitudes about data sharing have all played a role in the growth of this resource. Copyright (c) 2008 International Union of Crystallography urn:issn:0108-7673 Berman, H.M. 2008-01-01 doi:10.1107/S0108767307035623 International Union of Crystallography Since 1971, the Protein Data Bank archive of biological macromolecules has been a community-driven resource for science and education worldwide. en DATABASES; HISTORY OF PDB; NUCLEIC ACIDS; POLICY RELATIVE TO PDB; PROTEINS The Protein Data Bank began as a grassroots effort in 1971. It has grown from a small archive containing a dozen structures to a major international resource for structural biology containing more than 40000 entries. The interplay of science, technology and attitudes about data sharing have all played a role in the growth of this resource. text/html The Protein Data Bank: a historical perspective text 1 64 2008-01-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2008 International Union of Crystallography feature articles 88 95 http://scripts.iucr.org/cgi-bin/paper?pf0051 Copyright (c) 2007 International Union of Crystallography urn:issn:0108-7673 Röhr, C. 2007-07-01 doi:10.1107/S0108767307027250 International Union of Crystallography en BOOK REVIEW text/html Structure and chemistry of crystalline solids. By B. Douglas and S.-M. Ho. Pp. X + 346. New York: Springer 2006. Price (hardcover) EUR 106.95. ISBN 978-0-387-26147-8. text 4 63 2007-07-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2007 International Union of Crystallography book reviews 374 374 http://scripts.iucr.org/cgi-bin/paper?pf0034 Copyright (c) 2007 International Union of Crystallography urn:issn:0108-7673 Paufler, P.P. 2007-07-01 doi:10.1107/S0108767307021344 International Union of Crystallography en BOOK RECEIVED text/html The chemical bond in inorganic chemistry. The bond valence model. By I. David Brown. Pp. 278. Oxford: Oxford University Press, 2006. Price (paperback) GBP 35.00. ISBN 0-19-929881-5. text 4 63 2007-07-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2007 International Union of Crystallography books received 374 374 http://scripts.iucr.org/cgi-bin/paper?pf0948 Copyright (c) 2007 International Union of Crystallography urn:issn:0108-7673 Helliwell, J.R. 2007-09-01 doi:10.1107/S0108767307019125 International Union of Crystallography en BOOK REVIEW text/html Personal X-ray reflections. By U. W. Arndt. Pp. 177. Twickenham: Athena Press, 2006. Price GBP 6.99, USD 11.95. ISBN 1-84401-694-3. text 5 63 2007-09-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2007 International Union of Crystallography book reviews 439 440 http://scripts.iucr.org/cgi-bin/paper?sh9049 In the paper by Livet [Acta Cryst. (2007), A63, 63–87], equation (15) is incorrect. The correct equation is \beta(z) = \left\{\textstyle\sum\limits_{n = 0}^{\infty} (-1){}^n 2^{2n+2}z^{2n}/[(2n+1)(2n+2){}^2(2n+1)!]\right\}^2.\eqno(15) Copyright (c) 2007 International Union of Crystallography urn:issn:0108-7673 Livet, F. 2007-05-01 doi:10.1107/S0108767307016248 International Union of Crystallography Erratum to Livet [Acta Cryst. (2007), A63, 63–87]. en COHERENT X-RAY BEAMS; DYNAMICS OF FLUCTUATIONS; LENSLESS IMAGING; SMALL-ANGLE SET-UPS In the paper by Livet [Acta Cryst. (2007), A63, 63–87], equation (15) is incorrect. The correct equation is \beta(z) = \left\{\textstyle\sum\limits_{n = 0}^{\infty} (-1){}^n 2^{2n+2}z^{2n}/[(2n+1)(2n+2){}^2(2n+1)!]\right\}^2.\eqno(15) text/html Diffraction with a coherent X-ray beam: dynamics and imaging. Erratum text 3 63 2007-05-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2007 International Union of Crystallography addenda and errata 287 287 http://scripts.iucr.org/cgi-bin/paper?pf0045 Copyright (c) 2007 International Union of Crystallography urn:issn:0108-7673 Paufler, P. 2007-05-01 doi:10.1107/S0108767307011506 International Union of Crystallography en BOOK RECEIVED text/html Handbook of X-ray data. By G. Zschornack. Pp. IX + 967. Berlin: Springer-Verlag, 2007. Price (hardback) EUR 213.95. ISBN 978-3-540-28618-9. text 3 63 2007-05-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2007 International Union of Crystallography books received 288 288 http://scripts.iucr.org/cgi-bin/paper?sh5054 Copyright (c) 2007 International Union of Crystallography urn:issn:0108-7673 Spackman, M.A. 2007-03-01 doi:10.1107/S0108767307001298 International Union of Crystallography Comment on Volkov, King, Coppens & Farrugia [Acta Cryst. (2006), A62, 400–408]. en ASPHERICAL PSEUDOATOM MODEL; ELECTRIC FIELD; ELECTRIC FIELD GRADIENT; ELECTROSTATIC POTENTIAL text/html Comment on On the calculation of the electrostatic potential, electric field and electric field gradient from the aspherical pseudoatom model by Volkov, King, Coppens & Farrugia (2006) text 2 63 2007-03-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2007 International Union of Crystallography letters to the editor 198 200 http://scripts.iucr.org/cgi-bin/paper?sh0187 Copyright (c) 2007 International Union of Crystallography urn:issn:0108-7673 Volkov, A. Coppens, P. 2007-03-01 doi:10.1107/S0108767307002620 International Union of Crystallography Response to Spackman's comment on Volkov, King, Coppens & Farrugia [Acta Cryst. (2006), A62, 400–408]. en text/html Response to Spackman's comment on On the calculation of the electrostatic potential, electric field and electric field gradient from the aspherical pseudoatom model text 2 63 2007-03-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2007 International Union of Crystallography letters to the editor 201 203 http://scripts.iucr.org/cgi-bin/paper?dm5003 The general approach for describing and designing complex hierarchical icosahedral structures is discussed. Structural models of icosahedral carbon nanoparticles in which the local arrangement of atoms is virtually identical to that in diamond are derived. It is shown that icosahedral diamond-like particles can be transformed into onion-like shell structures (and vice versa) by the consecutive smoothing (puckering) of atomic networks without disturbance of their topological integrity. The possibility of coherent coexistence of icosahedral diamond-like core with onion shells is shown. Copyright (c) 2007 International Union of Crystallography urn:issn:0108-7673 Shevchenko, V.Ya. Madison, A.E. Mackay, A.L. 2007-03-01 doi:10.1107/S0108767307002723 International Union of Crystallography In icosahedral carbon nanoparticles, the diamond-like core can undergo a reversible topological transition into and coexist coherently with the onion shells. en CARBON ONION; COHERENT COEXISTENCE; NANODIAMOND The general approach for describing and designing complex hierarchical icosahedral structures is discussed. Structural models of icosahedral carbon nanoparticles in which the local arrangement of atoms is virtually identical to that in diamond are derived. It is shown that icosahedral diamond-like particles can be transformed into onion-like shell structures (and vice versa) by the consecutive smoothing (puckering) of atomic networks without disturbance of their topological integrity. The possibility of coherent coexistence of icosahedral diamond-like core with onion shells is shown. text/html Coherent coexistence of nanodiamonds and carbon onions in icosahedral core-shell particles text 2 63 2007-03-01 Acta Crystallographica Section A: Foundations of Crystallography Copyright (c) 2007 International Union of Crystallography research papers 172 176 http://scripts.iucr.org/cgi-bin/paper?sh5049 Methods for carrying out coherent X-ray scattering experiments are reviewed. The brilliance of the available synchrotron sources, the characteristics of the existing optics, the various ways of obtaining a beam of controlled coherence properties and the detectors used are summarized. Applications in the study of the dynamics of speckle patterns are described. In the case of soft condensed matter, the movement of inclusions like fillers in polymers or colloidal particles can be observed and these can reflect polymer or liquid-crystal fluctuations. In hard condensed-matter problems, like phase transitions, charge-density waves or phasons in quasicrystals, the study of speckle fluctuations provides new time-resolved methods. In the domain of lensless imaging, the coherent beam gives the modulus of the sample Fourier transform. If oversampling conditions are fulfilled, the phase can be obtained and the image in the direct space can be reconstructed. The forthcoming improvements of all these techniques are discussed. C