Hi Sun, On Mon, Feb 04, 2008 at 02:15:05PM -0800, Sun Tang wrote: > I used NCS before rigid body refinement. After that I did not put > NCS restraints in the restrained refinement and TLS+restrained > refinement because it raised the R/Rfree quite a lot.
Use NCS. Really! There is never a reason for switching off NCS restraints (ok _maybe_ at real atomic or ultra-high resolution ...). Obviously, you'll need to change the way you apply NCS restraints: from a simple per-chain definition to maybe a per-domain definition, taking out residues in crystal contacts, allowing for a different base B-factor of different chains/domains etc. Some programs do these things fairly automatically for you. This might make it awkward to use NCS sometimes, but at 2.8A it is a must (I think). And if your use of NCS increases Rfree, then there is aproblem in the setup of NCS restraints, not in the principal usage. Note: re-introducing NCS restraints might increase the R, but if the Rfree stays similar: who cares? -------------------------------------------------------------- See also: G J Kleywegt, "Use of non-crystallographic symmetry in protein structure refinement", Acta Crystallographica, D52, 842-857 (1996). According to http://xray.bmc.uu.se/~gerard/citation.html a "classic!" paper [gosh ... I really like Gerard's style ;-)]. Cheers Clemens -- *************************************************************** * Clemens Vonrhein, Ph.D. vonrhein AT GlobalPhasing DOT com * * Global Phasing Ltd. * Sheraton House, Castle Park * Cambridge CB3 0AX, UK *-------------------------------------------------------------- * BUSTER Development Group (http://www.globalphasing.com) ***************************************************************
