I would not sharpen structure factors before refinement. It may cause problems with B value refinement (a lot of B values may stuck around 2 or minimum B). One must remember that not all atoms in crystal have same Bvalue. There is a distribution of Bvalues.
However maps can be sharpened after refinement. It can be done directly in coot (I hope this version of coot is now widely available). Or if you are using refmac for refinement you can use: mapc sharpen # regularised map sharpening. Bvalues and regularisation parameters are calculated automatically or mapc sharpen <Bvalue> # regularised map sharpening with specified Bvalue or mapc sharpen <Bvalue> mapc sharpen alpha <value=0.1> # regularisation paramater. alpha=0 is simple sharpening. I am sure other programs have similar options. (I know CNS has and it has been used successfully by many people) regards Garib P.S. These options available from refmac v5.6 available from; www.ysbl.york.ac.uk/refmac/data/refmac_experimental/refmac5.6_linux.tar.gz On 25 Feb 2011, at 23:57, Dima Klenchin wrote: > At 05:39 PM 2/25/2011, Pete Meyer wrote: >>> Or could anyone suggest a program that would be of help? >> >> CAD scaling with a scale factor of 1.0 and negative B-factor (isotropic or >> anisotropic) should do the trick. I haven't had much luck with density >> sharpening (at least at ~4-5 Angstroms), but others have apparently had some >> success with it. > > Alternatively, CCP4i task Run FFT does the job: > > 1. Take MTZ from Refmac output > 2. Run FFT to create simple map with SigmaA-weighted phases (i.e., PHWT > label). > 3. In Infrequently used options, "Apply B-factor scaling to F1", specify > negative B-factor scaling value, usually within -10 to -50. > > - Dima
