Philiadelphia, PA, July 2015
The following report is a digest of more complete reports of the 2015 ACA Meeting in Philadelphia published in the ACA RefleXions of Fall 2015.
The meeting began with workshops on Serial Crystallography Data Analysis, Rietveld Refinement, and Small Angle Scattering. The Opening Reception was hosted by the exhibitors on Saturday evening.
The B. Warren Award for 2015 was presented to Laurence Marks. Gregory Petsko received the M. J. Buerger Award, and Yan (Jessie) Zhang received the Margaret C. Etter Early Career Award. Juan Manuel García-Ruiz delivered a plenary lecture 'The Impact of Crystals and Crystallography in Art and Culture' and screened his documentary film 'The Mystery of the Giant Crystals' filmed in the Naica mine in Mexico where transparent single crystals of gypsum as long as 11 m were discovered. Cora Lind-Kovacs and Robin Rogers chaired the Transactions Symposium, Crystallography for Sustainability.
The ACA's annual Awards Banquet featured the Past President's Address by Martha Teeter. The 2015 Class of ACA Fellows was introduced at the banquet by ACA President Chris Cahill. The fellows are Zbigniew Dauter, David Eisenberg, Hakon Hope, John Helliwell, Tom Koetzle, and David Rose. Cahill presented the ACA Service Award to Ilia Guzei. The ACA honored this year's 14 Poster Award Winners.
The B. Warren Award was awarded to Laurence Marks, Professor of Materials Science and Engineering at Northwestern U., for 'his contributions to electron crystallography and surface science, using both electron and X-ray diffraction'. Marks and his students have used electron microscopy to examine a number of metal oxide surfaces and have developed techniques that allow exquisite structural descriptions of these systems. He provided an atlas of elegant reconstructed surfaces that have been found and structurally characterized for different lattice planes from a single material, SrTiO
The M. J. Buerger Award for 2015 was awarded to Gregory Petsko, Arthur J. Mahon Professor of Neurology and Neuroscience at Weill Cornell Medical College, USA. The award citation reads, 'Petsko has made contributions of exceptional distinction to the study of proteins and enzyme mechanisms by X-ray crystallography, to the application of Structural Biology to the medical sciences, to the training and education of researchers and undergraduate students, to the mentoring of a generation of Structural Biologists, and to the research community in general, through service on government and other advisory boards and committees, and through his unique communication skills to the broader scientific community and the lay public'. Petsko's Award lecture was at times moving and inspirational as it featured the career of Tom Alber who passed away from Lou Gehrig's disease. Tom, Greg's first graduate student at MIT, later became professor at the U. of California, Berkeley and was a renowned crystallographic presence in his own right. Not incidentally, Greg now directs an institute dedicated to the elucidation and potential treatment of neurological diseases, one of which ultimately claimed Tom's life. In addition to his expressed admiration for Tom, Greg's lecture was rich with praise for the many collaborators and students who marked his research career. He reserved particular appreciation for his long-time research partner Dagmar Ringe and collaborator Ilma Schlichting. Many of the methods used today were invented in Greg's laboratories at MIT and Brandeis U. The lecture included an extended discourse on how these approaches were employed to work out the enzymatic pathway of P450 and the importance of concepts like the glass transition temperature and the intrinsic flexibility of proteins and enzyme active sites. The methodologies initiated and developed in Greg's laboratory have been recognized as major contributors to our understanding of enzymatic catalysis. Indeed, in enzymology today, a knowledge and detailed understanding of the underlying molecular structure as derived by X-ray crystallography is the first imperative. Greg finished his talk by suggesting that caution in interpreting cryogenic structures was certainly in order, and that it would be appropriate if all macromolecular structures deposited in the Protein Data Bank were to be accompanied by structures determined at room temperature, and suggested that this might be possible using the free-electron laser source.Alex McPherson
Transactions symposium: Crystallography for sustainability
The symposium focused on crystallographic research related to reducing energy consumption, protecting the environment, or providing greener synthesis of materials. L. MacGillivray (USA) discussed the solid-state synthesis and photodimerization of resorcinol co-crystals and showed that halogens or hydrogen bonding could be exploited to produce photostable co-crystals. T. Friščič (Canada) described mechanochemical solid-state synthesis without any solvents. H. zur Loye (USA) has developed a low-temperature two-step hydrothermal method to prepare hybrid materials with improved yield. A. Huq (USA) showed how powder neutron diffraction can elucidate the pathways of lithium, hydrogen or oxygen atoms in energy materials and determine site occupancies, including those responsible for ionic conductivity. The distribution of vacancies and anisotropic displacement parameters of light atoms that indicate the direction of ionic movement can give insights into underlying mechanisms and help optimize materials. P. Kalifah (USA) described powder diffraction studies of semiconductors that catalyze solar water splitting. H. Kleinke (Canada) described studies of thermoelectric materials that convert waste heat into electricity. Advanced thermoelectrics are heavily doped, narrow-gap semiconductors with heavy elements and complex crystal structures. Holger's group uses crystallography to correlate compositional changes with thermoelectric properties. They have tripled the thermoelectric figure-of-merit of some materials.Cora Lind-Kovacs and Robin Rogers
1.1.1. Crystallography of emergent phenomena
The session showcased crystallographic determinations of the structures of 'complex' materials having properties that emerge from the collective interaction of the components of the complex. K. Taddei (USA) combined X-ray and neutron powder diffraction to follow phase transitions from high to low symmetry and back in iron-based superconductors as a function of temperature and composition. The result was a complex phase diagram with two types of magnetism competing against superconductivity and each other. The two prevailing theories may explain the observed magnetism: either the physics is dominated by local-type interactions or by delocalized band-like physics. Since the latter implies wave-like states that might destructively interfere, Mössbauer spectroscopy was used as a local probe to look for 'nodes' where the component wavefunctions cancel one another out, so that there is no effective magnetic field. Exactly 50% of the iron sites were shown to be non-magnetic as predicted by the magnetic wave-like model. This highlighted the importance of combining careful diffraction experiments with complementary local probes.Jared Allred
1.1.3. Application of SANS/SAXS to structural biology
W. Heller (USA) reported on small-angle neutron scattering (SANS) studies of the Sinbidis virus, light harvesting complex II, bacterial photosystem I, and antimicrobial peptides, to illustrate how contrast variation methods using isotopic exchange and neutron scattering experiments achieve insights not accessible by other approaches. S. Sinha (USA) presented research on the structure and function of a key component of the autophagy nucleation complex that is involved in the degradation and recycling of damaged or harmful cytoplasmic components. Combining bioinformatics, X-ray crystallography, SAXS, circular dichroism, and molecular dynamics revealed the presence of a transient structure that changes into an ordered arrangement upon binding to a partner. N. Sekulic (USA) described contrast variation studies of centromeric mononucleosomes. Centromeres, vital to the proper segregation of chromosomes, are defined by a variant histone protein called CENP-A and slightly A-T rich repetitive DNA sequences. Using analytical ultracentrifugation and SANS contrast variation, a more extended conformation of CENP-A derived nucleosomes in solution was determined relative to the canonical form. These results reveal the role of DNA in the physical basis of how the CENP-A histone distinguishes centromeres from the rest of chromatin. J. Trewhella (Australia) described studies of proteins from HIV, including HIV reverse transcriptase and matrix (MA) interacting with calmodulin. Complementary information from solution scattering, crystallography, hydrogen-exchange mass spectrometry, and fluorescence provides insights into the structure and dynamics of these proteins. A. Round (France) reported on innovations at the synchrotron SAXS beam line BM29. In situ crystallization of glucose isomerase was performed to show that crystals could be grown and transported within the droplets, allowing for the study of nucleation in different additive conditions. S. Krueger (USA) applied SANS and contrast variation to the study of disordered proteins in two-subunit complexes. Using the program SASSIE, Monte Carlo sampling of backbone dihedral angles within protein models was used to generate ensembles of energetically relevant conformations for the disordered regions of the complex, using structural models that satisfy the contrast variation data. J. Curtis (USA) gave a progress report on the CCP-SAS initiative, an NSF-funded joint UK/USA collaboration to produce a new generation of open-source software to facilitate the atomistic modeling of macromolecules using SANS/SAXS data.Kushol Gupta and Alvin Acerbo
1.2.1. From fingerprinting to full ID: PXRD
This session was intended to bring new aspects of the use of powder diffraction to a more general audience with support from Bruker AXS, PANalytical, and Rigaku/Oxford Diffraction. A. Brunskill (USA) demonstrated the power of PXRD to characterize compounds relevant to the pharmaceutical industry. S. Bates (USA) spoke of the ability of PXRD to perform quantitative analyses on component mixtures, emphasizing the use of the chemometric method. J. Quinn (USA) discussed the use of conventional PXRD instrumentation to perform Pair Distribution Function (PDF) studies for the analysis of non-crystalline materials. PDF can provide a new method of analysis in PXRD. R. Suryanarayanan (USA) is using PXRD to understand the chemistry and effects of pressing drugs into pellets. J. Britten (Canada) provided an overview of how one can use single-crystal diffractometers and area detectors to perform PXRD experiments.Richard Staples
1.2.2. Engaging undergraduates with crystallographic research
Speakers focused on how to incorporate X-ray crystallography into the undergraduate curriculum, and how to launch a successful research program at an undergraduate institution. A. Nazarenko (USA) uses crystals of sweeteners of everyday products to show non-chemistry majors how useful information on molecular structure may be obtained through X-ray crystallography. C. Phillips-Piro (USA) discussed using X-ray crystallography to study the interaction of non-natural amino acids with proteins and explored the key factors in setting up and running a protein crystallography lab at an undergraduate institution. J. Golen (USA) described acquisition of a diffractometer through the NSF-MRI program to establish a regional resource in southeast Massachusetts and gave examples of undergraduate research results that are being obtained. D. Johnston (USA) described using mini research projects, based on student proposals, to characterize coordination compounds with his inorganic chemistry class and undergraduate research students. P. Cook (USA) discussed the challenges he faced in setting up a macromolecular crystallography research program at an undergraduate institution. J. Tanski (USA) gave a description of his research program in titanium-mediated asymmetric catalysis with crystal structures obtained at all stages of the project.Joe Tanski and Roger Rowlett
1.3.1. Career odyssey
The four panelists, C. Lind-Kovacs, C. Beavers, C. MacElrevey and S. Sheriff, described their careers, the responsibilities in their current positions and what has helped them succeed. C. Lind-Kovacs, a Professor at U. Toledo, USA, who teaches undergraduates and mentors graduate students and postdocs, suggested that postdocs aspiring to an academic career should learn people-management skills and seek mentors who are more experienced than they are. When asked, 'What is one thing you wish you were taught in graduate school?', Cora replied, 'Nobody taught me how to teach'. What Cora especially likes about her job is flexibility to set her own schedule. C. Beavers is a beamline scientist at ALS. The one thing she wishes she was told in graduate school is, 'Graduate school is not about what you learn, it's about learning to learn and learning to network'. Christine says her job is never boring, allows her to meet new beam line users, and requires her to travel all over. C. MacElrevey is a pharmacokineticist at Nuventra Inc., a contract research organization, and has established an LLC consulting company. She enjoys the 'variety' in her job and the satisfaction of helping others to achieve research goals. Celeste urges students to try new things and never give up. S. Sheriff, a senior research fellow at Bristol-Myers Squibb, suggested that being flexible is important to survival. He also suggested that managing people is a part of any job and one should learn how to do that well. Steve enjoys doing science and discovering what is not known.Smita Kakar
2.1.2. Crystal engineering form and function
This session addressed current research in the field of crystal engineering, with an emphasis on the relationship between the structure and the function of crystalline forms. N. Seeman (USA) created the field of DNA-based nanotechnology and has won numerous prestigious awards including the Kalvi Prize of 2014. His lecture attracted a huge audience who got a glimpse of his outstanding work in generating wide-open and programmable structures based on self-assembled DNA-based building blocks. N. Bathori (South Africa) discussed pharmaceutical applications, showing some fascinating structures and clear trends between melting points and solubility, which promise to place us closer to a rational design of crystals with desired pharmaceutical properties. J. Benedict (USA) presented pioneering work on combining the modular and open structures of MOFs with the photoswitchable behavior of diarylethylenes. Jason presented a structurally challenging new family of switchable MOFs accomplished by a unique combination of organic synthesis and coordination-driven self-assembly.Peter Wood and Tomislav Friščič
2.1.3. General interest I
This session highlighted recent developments in instrumentation and software technology. M. Ruf (USA) described the APEX3 software package, including the new structure solution and refinement plugin and improved twin-handling tools. A. Kleine (Gemany) described their microfocus X-ray sources and scatterless pinholes and what it takes to upgrade existing systems to these technologies. E. Espes (Sweden) talked about liquid metal jet X-ray source technology and the use of a Ga-In alloy as the cup of liquid metal, that allows two wavelengths to be used in diffraction experiments on the same instrument. With brilliances close to those of first-generation synchrotron sources, protein data can be collected in-house to nearly the same resolution as synchrotron data (1.85 versus 1.75 Å). C. Campana (USA) presented examples of analyses completed with the metal jet system on a Bruker D8 Venture. Z.-Q. Fu (USA) described shutterless data collection with a CCD detector to extract an extremely weak native SAD signal. B. Toby (USA) highlighted the improved user interface and graphing capabilities of GSAS-II, as well as the dual powder and single-crystal and dual X-ray and neutron diffraction refinement capabilities.Stacey Smith
2.1.4. Publication practices
This year's Publication Practices session focused on small-molecule crystal structures. Suzanna Ward (USA) drew attention to thousands of unpublished 'zombie' structures. She encouraged the use of the CCDC private-communication mechanism to bring the zombies to life. Information about zombie deposition is at: www.ccdc.cam.ac.uk/Community/Depositastructure/Pages/StructureDepositionInformation.aspx.
S. Blake (UK), Section Editor at Acta Cryst. Section B, described significant restructuring of the contents, formats and focus of all IUCr Journals. For example Section C, which has been rebranded as 'Structural Chemistry', now has lead articles, feature articles and scientific comment. It has a more flexible submission process that includes the use of Word and OpenOffice documents for the text. This removes an earlier requirement to include all text, including rich text, in the CIF, which led authors to publish elsewhere. T. Spek (Netherlands) urged that unmerged reflection data be deposited to permit any unusual features of the structure and claims of unexpected chemical features to be investigated in detail. Ton demonstrated his point with examples.Kimberly Lincoln and Larry Falvello
To be continued in the next issue, Volume 24, Number 2.