The STARANISO Server Anisotropy of the Diffraction Limit and Bayesian Estimation of Structure Amplitudes

The following results were obtained from the deposited data for PDB entry 4XYI.

The first pair of images below shows the OpenAstexViewer displays of the intensity data in 3D reciprocal space (the local mean I/σ(I) on the left and the Debye-Waller factor on the right).

The next row of 3 images shows the model and maps for a helical peptide ligand (H4) that is an important part of the structure.  The deposited model has its main-chain coloured green, while the STARANISO/BUSTER-re-refined model main-chain is coloured purple.  The electron-density maps are respectively:

• Left panel: the map produced by BUSTER structure-factor calculation from the deposited data;

• Middle panel: the map produced by BUSTER refinement from the deposited data;

• Right panel: the map produced by BUSTER refinement from the corrected data produced by STARANISO.

All maps were contoured at 1 RMSD, corresponding to absolute contour levels of 0.130Å^-3 (left), 0.124Å^-3 (middle) and 0.178Å^-3 (right).

Rwork/Rfree are 0.209/0.233 (left), 0.186/0.226 (middle) and 0.182/0.222 (right).

Note the 'BUSTER bonus' going from left to middle, and then the 'STARANISO bonus' going from middle to right.

The next pair of images shows the reciprocal-space correlation plots from the BUSTER refinements, on the left before correction by STARANISO and on the right, after.  Note how at high values of d* the completeness (yellow) goes down in the 'after' plot but the fit of the remaining data to the model is much better.  Also the observed correlation (red) and expected correlation (blue) plots agree much better.