Dear Phil, What is the space group? Could it be that the 4th monomer makes also a trimer by symmetry, in an alternative SG?
A. > On 10 Dec 2020, at 14:49, Phil Jeffrey <pjeff...@princeton.edu> wrote: > > Preamble: > I have an interesting crystal form with 3 monomers (~400aa) at full occupancy > and apparently one at much reduced occupancy. It was built recently from > Se-SAD and was in moderately good condition: Rfree=32% for trimer, 2.6 Å. In > recent refinement cycles it became obvious that there was a 4th monomer in a > region of weaker/choppy 2Fo-Fc and Fo-Fc density that corresponded to a > "confusing" set of low-occupancy SeMet sites found by SHELXD and Phaser-EP. > The experimental map was bad in that region and was probably flattened during > density modification anyway, in retrospect. > > Question: > Phaser failed to find the 4th monomer after trivially finding the other 3 > with a recent version of the monomer. I'm wondering if there's a way to > indicate "this one is partial occupancy" to Phaser, or if there's a way to > improve the odds of success beyond just lowering the expected % homology. Or > if anyone has had success with other programs. This is perhaps a rare edge > case but I naively expected Phaser to work. > > In the end I used the weak SeMet sites to locate the monomer and the > occupancy appears to be around 0.32 in refinement. > > Cheers, > Phil Jeffrey > Princeton > > ######################################################################## > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 > > This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing > list hosted by www.jiscmail.ac.uk, terms & conditions are available at > https://www.jiscmail.ac.uk/policyandsecurity/ ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
