Re: [ccp4bb] R factor & R free struck

[Roger Rowlett]

As always, look at the crystal packing of the MR solutions. That is a quick way to reject incorrect space group solutions. I never realized Phaser had the issue you described with the SGALTERNATIVE setting, but to be honest, I've always run it in "manual" mode, i.e., I set up separate jobs in all the alternative space groups and check Z-scores and packing. It's a bear in P222 or C222 with all the possible re-indexed alternatives, but it works. It's only CPU time. Cheers. Steven Sheriff wrote: How certain are you of the space group? I ask because in all versions of PHASER that I have used to date, it chooses the space group (when SGALTERNATIVE is set) after placing the first molecule and with additional molecules it then assumes the space group result from the first molecule is the correct space group (the PHASER team is supposed to be rectifying this). While this is often the correct space group, I have seen several cases with both PHASER and other molecular replacement programs (e.g. AMoRe) where the correct space group only becomes evident after the placement of the second molecule. In particular, I have seen a case where after the first molecule was placed, one would have chosen P 21 21 2 on the basis of statistics provided, but after the second molecule was placed, it was clearly P 21 21 21. Steven -- Roger S. Rowlett Professor Department of Chemistry Colgate University 13 Oak Drive Hamilton, NY 13346 tel: (315)-228-7245 ofc: (315)-228-7395 fax: (315)-228-7935 email: rrowl...@mail.colgate.edu