Chris, First, I would try NCS restraints even at ~ 2 A.
Second, any outliers in your diffraction data set that might skew the R values? Third, have you checked that your refined bulk solvent model is reasonable? Axel On Feb 21, 2014, at 6:13 PM, Chris Fage <[email protected]> wrote: > Thanks for the assistance, everyone. > > For those who suggested XDS: I forgot to mention that I have tried Mosfim, > which is also better than spot fitting than HKL2000. How does XDS compare to > Mosflm in this regard? > > I am not refining the high R-factor structure with NCS options. Also, my unit > cell dimensions are 41.74 A, 69.27 A, and 83.56 A, so there isn't one > particularly long axis. > > I'm guessing the low completeness of the 1.65 angstrom dataset has to do with > obstacles the processing software encountered on a sizable wedge of frames > (there were swaths of in red in HKL2000). I'm not sure why this dataset in > particular was less complete than the others. > > Thanks, > Chris > > > On Fri, Feb 21, 2014 at 6:41 PM, Chris Fage <[email protected]> wrote: > Dear CCP4BB Users, > > I recently collected a number of datasets from plate-shaped crystals > that diffracted to 1.9-2.0 angstroms and yielded very nice electron > density maps. There is no major density unaccounted for by the model; > however, I am unable to decrease Rwork and Rfree beyond ~0.25 and > ~0.30, respectively. Probably due to the more 2-dimensional nature of > my crystals, there is a range of phi angles in which the reflections > are smeared, and I am wondering if the problem lies therein. > > I would be grateful if anyone could provide advice for improving my > refinement statistics, as I was under the impression that the > R-factors should be ~5% lower for the given resolution. > > A few more pieces of information: > -Space group = P21, with 2 monomers per asymmetric unit; > -Chi square = 1.0-1.5; > -Rmerge = 0.10-0.15; > -Data were processed in HKL2000 and refined in Refmac5 and/or phenix.refine; > -PHENIX Xtriage does not detect twinning, but hints at possible weak > translational pseudosymmetry; > -I was previously able to grow one atypically thick crystal which > diffracted to 1.65 angstroms with Rwork/Rfree at 0.18/0.22. > Unfortunately, the completeness of the dataset was only ~90%. > > Regards, > Chris >
