February 2026 - phenixbb - phenix-online.org

modeling mixed metal sites in ligand
by Arthur Glasfeld 10 Feb '26

10 Feb '26

I’m using Phenix to refine an EM-derived model that is a protein complex with a polyoxometallate (POM). The POM has the formula CoTiW11O40(8-), where the Ti and W (as bridged 6-coordinate oxometallates) form an cage around the Co(II) ion with overall Td symmetry. You can google “Keggin” and “POM" to get an idea of the shape. The published structure of the isolated POM modeled 11/12 occupancy of W at each oxometallate center, and 1/12 Ti. At 2.2 Å, our map shows no obvious placement for the Ti relative to the W centers. So far, for simplicity’s sake, we have used a ligand cif file that has 12 W centers in refinement (this was derived from the published crystal structure using Elbow). But to finalize the model, it seems important to acknowledge the presence of the Ti center. A few thoughts have come to us on how to proceed. We could simply annotate our model to indicate the presence of an unmodeled Ti center and continue with the current 12 W model or we could arbitrarily place a Ti ion in each POM (there are 4 in the complex). More realistically (?) we could place two POMs at each site - one containing nothing but W centers at 11/12 occupancy and one with nothing but Ti centers at 1/12 occupancy. But that generates two unrealistic ligands instead of one. The best thing to do would be to have a ligand cif file that has the atom occupancy built into it, but so far as I can tell, Phenix won’t accept that. I’ve also contacted the RCSB for advice, but would welcome any thoughts you all might have, especially if there’s a way to create an accurate ligand description. Thanks in advance, Arthur Glasfeld Mansoor Lab Oregon Health and Science University

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Concentric, alternating difference density blob
by Dan Richman 09 Feb '26

09 Feb '26

Hi Phenix folks, Have any crystallographers seen the phenomenon I've captured in these screenshots (linked below to save space), of concentric, semi-spherical, alternating layers of difference density? It seems to be localized at a valine side chain at the edge of the model and reflected across some two-fold symmetry. There's no heavy metal in the crystallization. Overall, the quality of the map and the model refinements are very good; everything has behaved as expected. We're just trying to diagnose this phenomenon and our searches for related descriptions have not yielded anything. https://livejohnshopkins-my.sharepoint.com/:f:/g/personal/drichma6_jh_edu/IgBkH0K7T1_0SL32jIPvr41DAYbp0ZSjTv_VH3TMb8bwd3s?e=CQgBnl Thanks! -- Dan Richman, PhD (he/him/his) Research Associate, James Berger Lab Dept of Biophysics and Biophysical Chemistry Johns Hopkins University School of Medicine mobile: 201-669-0967

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[Wmsm] LAST CALL for registration at the 7th ISMSM, Lisbon, 17-20 March 2026
by Jose Artur Brito 03 Feb '26

03 Feb '26

Dear colleagues, This is the final call for registration for the 7th International Symposium on Microbial Sulfur Metabolism (ISMSM), which will take place in Lisbon, Portugal, from 17–20 March, 2026. This meeting will bring together researchers from across the globe to explore the latest advances in microbial sulfur cycling - from molecular mechanisms to ecological and environmental perspectives. The meeting will include keynote talks, selected oral presentations, poster sessions, and opportunities for informal discussion and networking. We encourage you to register and submit your abstract until 13rd February 2026. https://wmsm.itqb.unl.pt/registration/ For more information visit: https://wmsm.itqb.unl.pt/ We look forward to welcoming you in Lisbon next March! The 7th ISMSM Organizing Committee Inês Cardoso Pereira, Filipa Sousa, José Artur Brito, Andreia Pimenta and Américo Duarte ismsm(a)itqb.unl.pt --

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Submit your IUCr 2026 abstract to microsymposium MS012
by dominika＠work.swmed.edu 03 Feb '26

03 Feb '26

Dear colleagues, We invite you to submit an abstract to Microsymposium MS012, "Next-generation validation metrics for macromolecular structures" at the 27th IUCr Congress (Calgary, Canada; August 11–18, 2026). Session time: Wednesday, August 12, 2026, 2:30–5:00 pm Invited speakers: Mariusz Jaskolski, Daisuke Kihara, Brinda Vallat This microsymposium will focus on emerging concepts, methods, and best practices for validating macromolecular structures across crystallography, cryo-EM, NMR, and integrative/hybrid modeling. We particularly welcome contributed talks that address challenges posed by increasing model complexity, heterogeneous data, and AI/ML-driven structure prediction. Topics of interest include (but are not limited to): ML- and AI-assisted validation and assessment Atomic-level precision, accuracy, and uncertainty metrics Cross-validation against experimental and orthogonal data Validation of ensembles, flexible models, and integrative structures Validation and QA pipelines used in community resources (e.g., PDB, CCDC) We look forward to receiving your abstracts! As part of our commitment to equity, diversity, and inclusion, we particularly encourage abstract submissions from women, early-career researchers, and members of groups historically underrepresented, in order to work together toward building a strong, inclusive, and well-balanced Congress. Please share widely with potentially interested colleagues. Abstract submission: https://event.fourwaves.com/iucr-2026/submission Deadline: February 15, 2026 (please check the submission site for updates) We would be delighted to receive your contributions and to see you in Calgary. With best wishes, Deborah Harrus & Dominika Borek

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