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Updated: Aug 20, 2026

Manganese Oxide Nanoparticle Synthesis by Thermal Decomposition of Manganese(II) Acetylacetonate
Published on: June 18, 2020
Going soft and SAD with manganese
Paula S Salgado1, Martin A Walsh, Minni R L Laurila
1Division of Structural Biology, The Henry Wellcome Building for Genomic Medicine, Oxford University, Roosevelt Drive, Oxford OX3 7BN, England.
Abstract:
SAD phasing has been revisited recently, with experiments being carried out using previously unconventional sources of anomalous signal, particularly lighter atoms and softer X-rays. A case study is reported using the 75 kDa RNA-dependent RNA polymerase of the bacteriophase phi6, which binds a Mn atom and crystallizes with three molecules in the asymmetric unit. X-ray diffraction data were collected at a wavelength of 1.89 A and although the calculated anomalous signal from the three Mn atoms was only 1.2%, SHELXD and SOLVE were able to locate these atoms. SOLVE/RESOLVE used this information to obtain SAD phases and automatically build a model for the core region of the protein, which possessed the characteristic features of the right-hand polymerase motif. These results demonstrate that with modern synchrotron beamlines and software, manganese phasing is a practical tool for solving the structure of large proteins.
Insights
Manganese phasing, using lighter atoms and softer X-rays, is now practical for solving large protein structures. This study demonstrates its effectiveness for RNA-dependent RNA polymerase structure determination.
Area of Science:
- Structural biology
- X-ray crystallography
- Protein structure determination
Background:
- Single-wavelength anomalous diffraction (SAD) phasing is crucial for determining protein structures.
- Traditionally, heavier atoms were used for anomalous signal, limiting applications.
- Recent advancements explore lighter atoms and softer X-rays for SAD phasing.
Purpose of the Study:
- To investigate the feasibility of manganese phasing for large protein structure determination.
- To showcase the application of SAD phasing with unconventional anomalous scatterers.
Main Methods:
- Collected X-ray diffraction data for bacteriophage phi6 RNA-dependent RNA polymerase at 1.89 A wavelength.
- Utilized SHELXD and SOLVE software to locate manganese atoms despite a low anomalous signal (1.2%).
- Employed SOLVE/RESOLVE for SAD phase calculation and automated model building.
Main Results:
- Successfully located three manganese atoms per asymmetric unit.
- Obtained SAD phases and built a partial protein model, revealing the right-hand polymerase motif.
- Demonstrated the utility of manganese phasing for a 75 kDa protein.
Conclusions:
- Manganese phasing is a practical method for solving large protein structures.
- Modern synchrotron facilities and software enhance the capabilities of SAD phasing.
- This technique expands the scope of X-ray crystallography for complex biological macromolecules.
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