NAME: Eleanor Dodson

AFFILIATION: University of York, UK

CONTACT: ccp4@ysbl.york.ac.uk

 

TITLE: "The Border between Molecular Replacement and the Experiment"

ABSTRACT: The talk will address the following issues.

1) It is important to know as much as possible of the biology of the system under study.

2) The sequence allows the search for homologues. It is important to identify and align as many as possible to highlight possible domain movement. Homologues are likely to have the same assembly. Knowing the likely biological molecule can speed up the search.

3) Once some crystal data is available, the cell and point group can be determined. From this the volume of the asymmetric unit can be found and some estimate made of the expected number of molecules to be positioned in the asymmetric unit.

4) It is as always important to check data quality and identify likely problems, such as anisotropy or twinning.

5) If there is more than on molecule in the asymmetric unit the data can reveal more information. Is there non-crystallographic translation? Is there twinning? Does the self-rotation indicate anything interesting?

6) Verification. Once a solution is found this can be checked against extra information.

7) Is the packing sensible?

8) Do the phases derived from the molecular replacement model allow anomalous scatterers to be identified and do they fit expectations?

9) If there are experimental phases do the maps show some modicum of agreement wit the MR model?

10) Refinement. Is there extra information which can help refinement proceed quickly and smoothly? Examples are: Careful rigid body analysis. Averaging maps using known NCS. Combining experimental and model phasing.