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spinqualitylabelsall models Caption for this structure Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D This is a default text for your page Sandobox 027 Test. Click above on edit this page to modify. Be careful with the < and > signs. You may include any references to papers as in: the use of JSmol in Proteopedia or to the article describing Jmol to the rescue. Molecular Tour 2026_09_24 test The Pyrococcus abyssi rubredoxin structure, with the mutations W4L and R5S was determined to 0.43 Å resolution and deposited in the Protein Data Bank as 30or for the independent atom model (IAM) refinement and 30oh for the transferable aspherical atom model (TAAM) refinement. Several technical advances were essential to achieve this high-quality, ultra high-resolution structure. The authors used a large, well-ordered crystal, with approximate dimensions of 600 x 500 x 300 micrometres in size, mounted in a Kapton loop and flash-cooled directly in liquid nitrogen. The dataset was collected at 100 K on the PETRA III P14 beamline at EMBL Hamburg @ DESY using a high-energy X-ray beam of 32.1 keV. The diffraction data were collected using a top-hat beam rather than a conventional focused beam. The beam was approximately 600 × 500 µm, collimated using compound refractive lenses and matched to the crystal. This allowed the entire crystal volume to be used for diffraction while minimizing background scattering from the surrounding liquid. The experiment used a high-Z detector, the DECTRIS EIGER2 CdTe 16M, which has improved detective quantum efficiency at the high X-ray energies required for sub-Ångström data collection. This detector allows a wide dynamic range and makes it possible to collect data across the full resolution range in a single experiment. Data collection was executed through the Global Phasing workflow integrated with MXCuBE on the P14 beamline. This enabled a carefully designed multi-orientation strategy that fills cusp regions in reciprocal space, avoids goniostat shadowing and distributes multiplicity more evenly than a single-orientation dataset. The workflow also feeds instrument-specific shadow information into the automated data-processing pipeline, autoPROC, which uses XDS, AIMLESS and STARANISO. The total dose was 500 kGy and the resulting dataset contained 6,545,565 total reflections and 245,905 unique reflections, with an average multiplicity of 26.6. In the outermost resolution shell, the data still had a CC₁/₂ of 0.621 and I/σ(I) of 1.7, indicating that the highest-resolution measurements remained meaningful. The structure of Pyrococcus abyssi rubredoxin at 0.43 Å resolution is one of the highest-resolution protein structures reported to date. The study is significant because it shows that, with sufficiently high-resolution data, the electron density in a protein can be interpreted not only in terms of atomic positions but also in terms of chemical bonding and valence electron distribution. When the structure was refined using standard spherical atom models in Global Phasing´s BUSTER, the independent atom model (IAM), strong positive difference density appeared at the midpoints of C–C, C–N and C–O bonds. This pattern is characteristic of deformation density, the redistribution of electron density associated with covalent bonding rather than a simple sum of spherical atomic densities. The key finding is that refinement using a transferable aspherical atom model (TAAM) by connecting the DiSCaMB library to BUSTER removes these positive features from the difference maps, confirming that they correspond to genuine electron-density deformations rather than model error or noise. In other words, the authors did not merely observe unexplained density; they showed that a chemically more realistic scattering model accounts for it. The publication associated with PDB entries 30or and 30oh is best understood as a milestone in the maturation of biological quantum crystallography. It does not simply report another high-resolution structure, it demonstrates that the technical obstacles once considered prohibitive — high-energy diffraction, low-dose multi-orientation data collection, high-Z detection, automated processing and aspherical refinement — can now be assembled into a reproducible workflow. The most important implications are that accurate electron-density studies of biological macromolecules are feasible, and that such data may provide direct structural insight into enzyme mechanisms, redox centers and other processes with a quantum-mechanical character. The Fe–S₄ cluster in rubredoxin, however, still shows residual density, highlighting that chemically complex metal sites may require even more detailed quantum-mechanical modelling. Overall, the study suggests that sub-Ångström crystallography is moving from a rare technical achievement toward a practical approach for studying the electronic structure of proteins, with particular relevance to enzyme catalysis and metal-cluster chemistry. Publication: https://doi.org/10.1107/S2059798326007448 Paknia, E., Flensburg, C., Chodkiewicz, M. L., Fogh, R. H., Keller, P., Vonrhein, C., Schulze-Briese, C., Dominiak, P. M., Bourenkov, G., Bricogne, G. & Chari, A. (2026): Towards routine accurate electron-density studies of biological macromolecules. Acta Crystallogr. D Struct. Biol., 82, published online 12.08.2026. This is a sample scene created with SAT to color by Group, and another to make a transparent representation of the protein. 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