Hi Matt, this can be done with SHELXL, even at 2-3A resolution. Anomalous data do help reduce the correlation between B-factor and occupancy (see e.g. https://doi.org/10.1126/science.1254840 to stick with Pavel's example)
SHELXL prints the correlation coefficient between occupancy and b-factor, and also the ESD of the occupancy. The is more reliable with least-square refinement, but for large structures, you may need a lot of RAM. PDB2INS (https://www.nature.com/articles/s41467-018-06957-w) conveniently prepares the INS-file from your PDB for you. Best wishes, Tim On Tue, 5 Sep 2023 19:31:25 +0100 Matt McLeod <mjmcleo...@gmail.com> wrote: > Hi all, > > I am trying to get some insight in the accuracy/precision of > occupancy refinements. I have done some 2-state occupancy > refinements and have observed the refinement achieving ~0.25-0.3 > occupancy for the minor population. This population, when observing > the electron density maps, had essentially no evidence for it being > present. I was wondering: > > What are the errors in the reported occupancies? > > Is there a lower and upper limit to occupancy refinements? As in, if > you occupancy refine two states and one is imaginary will it refine > to approximately 1 and 0? Or does the background noise always given > a positive number to the imaginary set? This would, to me at least, > be the lower and upper limits to the occupancy refinements and could > be used as a normalization factor for other atoms. Maybe my logic is > off... > > Any insight or literature would be appreciated! > Matt > > ######################################################################## > > 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/ -- -- Tim Gruene Head of the Centre for X-ray Structure Analysis Faculty of Chemistry University of Vienna Phone: +43-1-4277-70202 GPG Key ID = A46BEE1A ######################################################################## 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/
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